The proposed research is designed to study the mechanism of DNA initiation and replication using bacteriophage T4 infected E. coli as a model system. Emphasis are placed on the studies of phage gene products whose functions are needed during the on-set of DNA replication and they are defined by the DNA-delay phenotype. One of these proteins the product of gene 39 which serves as one of the positive determinants in regulating specific T4 DNA replication is chosen for detailed biochemical studies. We plan to purify this protein to apparent homogeneity in order to analyze its enzymology as well as the physical interaction with DNA. We also plan to identify and isolate the origin of T4 DNA replicati n, since the DNA sequences surrounding the origin(s) of replication are presumably the target sites for the action of initiation proteins which 39-protein may be one of them.